Germinação de sementes de Melanoxylon brauna (SCHOTT) sob diferentes temperaturas: aspectos morfofisiológicos e enzimáticos

• Autor(a) principal: Flores, Andressa Vasconcelos
• Data de Publicação: 2011
• Tipo de documento: Tese
• Idioma: por
• Título da fonte: LOCUS Repositório Institucional da UFV
• Texto Completo: http://locus.ufv.br/handle/123456789/558
• topic: Condutividade elétrica; Espécies arbóreas; Radicais livres; Deteriorização; Proteína; Electrical conductivity; Tree species; Free radicals; Deterioration; Protein; CNPQ::CIENCIAS AGRARIAS::RECURSOS FLORESTAIS E ENGENHARIA FLORESTAL::SILVICULTURA

The germination of tropical tree species needs more precise information on the physical and intrinsic factors that may interfere in the germination process. Given this fact, this study aimed to investigate the morphometric characteristics and increasing levels of temperature and its implications on the physiology and metabolism of Melanoxylon brauna Schott seeds during the germination process. To this end, the experiments were conducted at the Laboratory of Seed Analysis of Forestry in Department of Forestry, University Federal of Viçosa - UFV. The seeds used in this study were collected from 10 trees in the city of Leopoldina - MG. In the first chapter, two assays were conducted, the first to evaluate the effect of color and size, in which the seeds were visually classified into light and dark, and in relation to size in large and small, and then were sown in two pieces of filter paper. In the second assay, were evaluated the effect of different substrates on germination. Thus, were tested the substrates on sand (SA), between sand (EA), on paper germitest (SP), between paper germitest (EP) and paper roll germitest (RP). In both trials, seeds were placed in BOD under constant temperature of 25°C and constant light for 10 days, and evaluated the characteristics of germination speed index (GSI) and percentage of germination. In the second chapter were carried out three assays. In the first were determined curves of soaking at temperatures of 5, 10, 15, 20, 25, 30, 35, 40 and 45°C. In the second trial, to identify the cardinal temperatures, seeds were kept under each temperature for a period of 10 days in BOD, under constant light. For the third test, was carried out electrical conductivity test (EC) with the seeds incubated for 24, 48 and 72 hours of immersion in each of the temperatures mentioned above, and then they were placed in erlenmeyers with 75 mL deionized water at 25°C, for 24 hours for subsequent reading of conductivity. In the third chapter, enzymatic analysis was performed. Measurements of the activities of superoxide dismutase (SOD, EC 1.15.1.1), ascorbate peroxidase (APX, EC 1.11.1.11) and catalase (CAT, EC 1.11.1.6) were made in the micropylar endosperm and embryonic axis of seeds germinated under the same conditions described above, at temperatures of 15, 25, 30 and 40°C, and every 12 hours until the samples were taken root protrusion of 50% of the seeds or 168 hours to a temperature of 15°C. Seeds small and light have lower germination e IVG that the small and large, regardless of color. The substrate most suitable for the testing laboratory germination is the paper roll germitest. The temperature appeared significantly in germination and synchronization of Melanoxylon brauna seeds. The cardinal temperatures for germination (%) are: 12.3°C - minimum 30.0°C - optimal (theoretical) and 42.7°C maximum. The temperature ranges considering all the variables investigated were: 12.1 to 12.6°C (minimum); 30 to 35.8 ° C (optimum) and 42.4 to 43°C (maximum). The specie has a wide range of germination with respect to temperature, germination was observed in the temperature range from 12 to 42°C. The EC test was efficient to evaluate the effect of temperature on the physiology and according to this, the optimum temperature is 27°C. Did not detect the activity of SOD, APX and CAT in the micropylar endosperm during seed germination under different temperatures. In the embryonic axis, the activities of SOD and CAT showed greater changes along the germination when subjected to temperatures of 15 and 40°C. The APX enzyme activity in the embryonic axis was not affected by temperature during germination and its activity was extremely low.